Do we know what HIIT training actually is ?  And why it shot to stardom in the naughties ?

HIIT workouts are inspired by a piece of research performed by Japanese sports scientist Dr Izumi Tabatta in 1996.  (’Tabatta’ training is often used as an interchangeable term for HIIT training.)

Dr Tabatta’s research demonstrated  a greater caloric burn from shorter interval training, than from longer aerobic activity.  This was attributed to a phenomenon known as EPOC (Excess Post Exercise Oxygen Consumption) or known colloquially as ‘afterburn’.

However,  this is unfortunately based on a misunderstanding of the work that Dr Tabatta did:

In the actual study one group performed moderate intensity (70% VO2 max) aerobic activity for one hour, 5 days per week.  The other group performed a 10 minute moderate intensity (70%)  warm up followed by 7-8 sets of 20 seconds at 170% of VO2 max with 10 seconds rest – they performed this for four of the five days, and on the fifth they performed 30 minutes (70%) moderate intensity exercise.

(So worth noting that the HIIT training group performed 70 mins of aerobic activity ON TOP, of the interval work.)

The key point to understand is that VO2 max is measured by gradually increasing the resistance on a cycle ergometer whilst measuring their oxygen uptake.  The point at which the persons oxygen uptake no longer increases is measured as their VO2 max – in other words complete exhaustion and often accompanied by nausea.  So in this study that point was reached, and then resistance/ work rate increased another 70%!

You can imagine how mentally and physically demanding that would be to reach a point of exhaustion, and then push that far beyond it.  It’s a performance level that Olympic cyclists , rowers, and triathletes may reach – but very few others are capable of.

The simple facts are that a bodyweight routine of burpees, star jumps and treadmill sprits (however tough it may feel) is no where near the level of intensity that was created in Dr Tabatta’s lab that created the famed ‘afterburn’ effect.

Should you be within the small percentage of the elite population who can achieve 170% of Vo2 max effort,   by definition, it physiologically cannot be sustained for a 45 minute exercise class.

True bouts of HIIT  – as per the original study – can be achieved by very few, and even then repeated for only a few minutes. In those rare cases where it can be achieved, HIIT training requires a significant amount of time to recover from.

In short – gym classes are not HIIT training.

Unfortunately there aren’t shortcuts when it comes to health and fitness,  and whilst short sharp interval based workouts absolutely have a place.  They should make up just one small part of a balanced exercise regime.

A well structured program should include elements addressing all five measurable ‘pillars’ of fitness:

The quantity, frequency, and emphasis placed on each of these five pillars will depend upon the individuals starting point, and their specific wants, goals and needs (bearing in mind that a persons wants can be different to their needs, a good trainer should have the skills to strike this balance!)

I will typically start my clients off on two full body resistance training sessions per week,  two low intensity cardio sessions, and one shorter interval based session.   Depending upon specific goals I may then switch one of the low intensity cardio sessions for an additional resistance workout.

This has become a bit of a taboo subject in the health and fitness world!

Whilst aesthetics dent tend to be the most satisfying or quantifiable of goals,  training to improve body composition for health reasons is still a valid reason to exercise, especially in this COVID-19 era.

Unfortunately, planned exercise makes up only around 10% of our daily calorific expenditure – so even if HIIT classes did what they said on the tin (or the studio brochure), (which they don’t), then you would still need to address energy balance and protein intake (in other words, diet!) in order to create changes to body composition  – whether that is fat loss or muscle gain.

When it comes to improving any of the measurable health markers a combination of resistance training, low intensity cardio and a small amount of high intensity cardio is by a considerable margin, the most effective, efficient and sustainable method.

Quick fixes and endorphin hits are easier to sell than slow sustainable moderate changes to diet and lifestyle!

Easier to sell, however, does not correlate with effectiveness.

The trend hasn’t, in my opinion, come from any form of malfeasance.  Rather it has come from misunderstanding.

When the only criteria that a gym or a studio has for its product is to get sweaty and have fun  – then that is what its trainers and instructors will deliver!  And there will never be any shortage of trainers wanting to deliver that (because its easy),  or whilst misinformation is so prevalent no shortage of consumers wanting to participate  (because its fun!).

However,  if you manage and deliver it well – programs that give results can be fun too.